Electronics device, semiconductor device, and method for manufacturing the same

ABSTRACT

It is an object of the present invention to provide a high reliable EL display device and a manufacturing method thereof by shielding intruding moisture or oxygen which is a factor of deteriorating the property of an EL element without enlarging the EL display device. 
     In the invention, application is used as a method for forming a high thermostability planarizing film  16 , typically, an interlayer insulating film (a film which serves as a base film of a light emitting element later) of a TFT in which a skeletal structure is configured by the combination of silicon (Si) and oxygen (O). After the formation, an edge portion or an opening portion is formed to have a tapered shape. Afterwards, distortion is given by adding an inert element with a comparatively large atomic radius to modify or highly densify a surface (including a side surface) for preventing the intrusion of moisture or oxygen.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to a semiconductor device having a circuitincluding a thin film transistor (hereinafter referred to as a TFT), andto a method for manufacturing the same. For example, the inventionrelates to an electronics device on which an electrooptical devicetypified by a liquid crystal display panel or a light emitting displaydevice having an organic light emitting element is mounted as itscomponent.

In this specification, the term semiconductor device refers to a devicein general that utilizes semiconductor characteristics to function, andelectro-optical devices, semiconductor circuits and electronics devicesare all included in the semiconductor device.

2. Description of the Related Art

In recent years, a technique for forming a thin film transistor (a TFT)by using a semiconductor thin film (thickness is about from several nmto several hundreds nm) formed over a substrate having an insulatingsurface has drawn attention. The thin film transistor has gained a wideapplication in electronics devices such as an IC and an electroopticaldevice, and particularly, development of a TFT as a switching elementfor an image display device has been hurriedly carried out

In order to obtain a high quality image in an image display device, Anactive matrix liquid crystal display device and an active matrix lightemitting device as image display devices in which pixel electrodes arearranged in matrix and TFTs as switching elements connected to therespective pixel electrodes are used have drawn an attention.

Such an active matrix display device has been expanded in application.Therefore, the device is required to have high resolution, high openingratio, and high reliability with the increase in a screen size.

It is possible to form a pixel portion that performs image display, anda driver circuit for controlling a pixel portion such as a shiftregister circuit, a level shifter circuit, a buffer circuit, a samplingcircuit, or the like based on a CMOS circuit in each functional block,over a single substrate for a liquid crystal module mounted on a liquidcrystal display device.

Further, in the pixel portion of the liquid crystal module, a TFT (apixel TFT) is arranged in each of several tens to several millions ofpixels and each pixel TFT is provided with a pixel electrode. A counterelectrode is provided on a counter substrate side so that a liquidcrystal is interposed between the two electrodes, to thereby form a kindof capacitor with the liquid crystal used as a dielectric. A voltageapplied to each pixel is then controlled by a switching function of theTFT to control the application of charge to the capacitor. Thus, theliquid crystal is driven, thereby displaying an image through thecontrol of an amount of transmitted light.

In a liquid crystal display device, when a pixel electrode is formedover an interlayer insulating film having unevenness, unevenness is alsoformed on the surface of the pixel electrode along the unevenness of theinterlayer insulating film. The uneven portion has a possibility tocause an orientation defect of a liquid crystal.

In recent years, research related to a light emitting device having anEL element as a self-luminous light emitting element has been activated.The light emitting device is also referred to as an organic EL displayor an organic light emitting diode. Since these light emitting deviceshave characteristics such as rapid speed of response that is suitablefor movie display, low voltage, low power consumption driving, theyattracts an attention for a next generation display including a newgeneration's cellular phone and a personal digital assistance (PDA).

As for the EL element, it is said that by sandwiching an organiccompound layer between a pair of electrodes and applying voltagetherebetween, an electron injected from a cathode and a hole injectedfrom an anode are recombined at luminescence center in the organiccompound layer to form a molecular exciton and when the molecularexciton returns to the ground state, energy is discharged to emit light.There are known singlet excitation and triplet excitation in an excitedstate, and it seems that light can be emitted by way of either of theexcited states.

There are an inorganic light emitting material and an organic lightemitting material as a light emitting material used for an EL element,and the organic light emitting material driven with low voltage drawsattention.

However, also in a light emitting device using an EL element, when ananode (or a cathode) is formed over an interlayer insulating film havingunevenness, there is a possibility that short is generated between theanode and the cathode since a layer containing an organic compound isthin.

Further, an organic EL element using an organic material for an ELelement has a problem that luminescence properties such as luminance orevenness of luminescence significantly deteriorate compared to an earlyperiod. The low reliability is a factor causing the practicalapplication to be limited.

As one factor of worsening reliability, moisture or oxygen whichintrudes into the organic EL element from outside is given.

In an EL display device (panel) using an EL element, moisture intrudinginside cause a severe reliability lowering to generate a dark spot,shrink or luminance deterioration from the periphery of a light emittingdisplay device. The dark spot is a phenomenon in which luminancedeteriorates partly (including a pixel which does not emit light). Thedark spot is generated when a hole emerges on an upper electrode, forexample. Shrink is a phenomenon in which luminance deteriorates from anedge of a pixel.

Accordingly, a display device having a structure for preventing theabove-mentioned deterioration of the EL element has been developed. Inorder to prevent the foregoing problems, there is a method in which theEL element is stored in an airtight container to shield from outside airby sealing the EL element in the enclosed space, and a desiccant isfurther provided separate from the EL element in the enclosed space (forexample, Reference 1: Japanese Patent Laid-Open No. Hei 9-148066).

Further, there is another method in which a sealant is formed over aninsulator with the EL element formed thereon, and an enclosed spacesurrounded by a covering member and the sealant is filled with a fillermade of a resin or the like; therefore, the EL element is sealed fromoutside (for example, Reference 2: Japanese Patent Laid-Open No. Hei13-203076).

In the above-mentioned references, a sealant is formed over an insulatorwith an EL element formed thereon, and an enclosed space surrounded by acovering member and the sealant is formed.

Briefly, moisture which causes deterioration such as a dark spotintrudes into a display device after sealing in most cases. In addition,moisture or oxygen intrudes mainly through the sealant since aninsulator and a covering material are made of metal or glass in mostcases.

When the sealant for sealing is on laminated films, all the laminatedfilms are to directly contact with atmosphere outside of a panel.Therefore, moisture or oxygen outside the panel intrudes inside thedisplay device through the laminated films. Further, when a materialhigh in moisture permeability and water-absorbing property such asacrylic is used as an interlayer film, intruding moisture or oxygen isincreased.

In addition, in the case of performing patterning of a partition wall,or an aperture step or a washing step of a contact hole after formingthe interlayer film, when the interlayer film has a water absorptionproperty, moisture is included inside the interlayer film during thesesteps.

Moisture or oxygen intrudes from an exterior surface of the interlayerfilm, then, intrudes into the interlayer film which is directly contactwith the EL element after going through a disconnection part and thelike generated by poorness of deposition property of source and drainelectrodes in the contact hole. Alternatively, moisture included in theinterlayer film intrudes into of the EL element. It is thought thatvarious deterioration such as internal contamination of an EL displaydevice, deterioration of electric property, a dark spot or shrink.

BRIEF SUMMARY OF THE INVENTION

It is an object of the present invention to provide a high reliable ELdisplay device and a manufacturing method thereof without enlarging theEL display device by shielding intruding moisture or oxygen, which is afactor of deteriorating the property of an EL element.

In addition, the invention provides an interlayer insulating film whichhas sufficient planarity and insulation in an insulating film havingplanarity used for a semiconductor device and in which moisture contentdoes not change even when a wet step is performed later.

In the invention, an interlayer insulating film which is high in heatresistance, insulation and planarization rate is required as aninterlayer insulating film provided for planarization. It is preferableto use application typified by spin coat as a method for forming such aninterlayer insulating film rather than CVD or vapor deposition.

In the invention, application is used as a method for forming a highthermostability planarizing film, typically, an interlayer insulatingfilm (a film which serves as a base film of a light emitting elementlater) over a TFT in which a skeletal structure is configured by thecombination of silicon (Si) and oxygen (O). After the formation, an edgeportion or an opening portion is formed to have a tapered shape.Afterwards, distortion is given by adding an inert element with acomparatively large atomic radius to modify or densify a surface(including a side surface) for preventing the intrusion of moisture oroxygen.

A solution ingredient is prevented from intruding into the highthermostability planarizing film or reacting when performing a step withthe use of liquid (referred to also as a wet step) later by adding aninert element and modifying a surface of the high thermostabilityplanarizing film. In addition, moisture or a gas is prevented from beingreleased from the inside of the high thermostability planarizing filmwhen a heat treatment step is performed later. Further, moisture or agas is prevented from being released from the inside of the highthermostability planarizing film by a change over time to enhancereliability of a semiconductor device.

In a liquid display device or a light emitting display device, acircumference of a display portion is surrounded by a sealant and sealedwith a pair of substrates. However, an interlayer insulating film of aTFT is provided over the entire surface of a substrate. Therefore, whena pattern of the sealant is described within a circumference edge of theinterlayer insulating film, there is a possibility that moisture or animpurity might intrude from a part of the interlayer insulating filmwhich is located outside the pattern of the sealant. Hence, thecircumference of the high thermostability planarizing film used as theinterlayer insulating film of the TFT is made within the pattern of thesealant, preferably, the edge portion of the high thermostabilityplanarizing film is covered with the sealant so as to overlap with thepattern of the sealant. Further, intrusion of moisture or oxygen isprevented by forming the edge portion of the high thermostabilityplanarizing film to have a tapered shape and adding an inert elementthere to highly densify. In addition, etching may be performed forselectively forming only the edge portion of the high thermostabilityplanarizing film to have a tapered shape.

The first configuration of the invention disclosed in this specificationis a light emitting device including a display portion which is formedby arranging light emitting elements between a pair of substrates,wherein the light emitting elements are formed over a highthermostability planarizing film formed over one substrate, and the pairof substrates are fixed to each other with a sealant surrounding acircumference of the display portion, and an edge portion of the highthermostability planarizing film has a tapered shape, and is added withan inert element.

In addition, in a liquid crystal display device or a light emittingdisplay device, an opening which serves as a contact hole is formed inan interlayer insulating film. Therefore, a solution ingredient intrudesinto the interlayer insulating film or reacts when wet etching orpurified water washing is performed in patterning of a wiring performedafter forming the opening. Therefore, it is preferable to preventintrusion of moisture or oxygen by highly densifying a side surface ofan opening portion by adding an inert element, after forming an openingin the high thermostability planarizing film. Then, patterning of awiring is performed. In the invention, a step of forming an opening inthe high thermostability planarizing film to have a tapered shape isperformed simultaneously with a step of forming an edge portion of thehigh thermostability planarizing film to have a tapered shape, then,modified by entirely adding an inert element thereto.

In the invention, the method for forming an interlayer insulating filmby application is shown in the following. Initially, thinner pre-wettreatment is performed to improve wettability after performing washingwith purified water. Then, a liquid raw material called varnish in whicha low molecular weight ingredient (a precursor) having the combinationof silicon (Si) and oxygen (O) is dissolved into a solvent is appliedover the substrate by spin coat or the like. Afterwards, an interlayerinsulating film can be obtained as a thin film by conductingvolatilization (evaporation) of a solvent and crosslinking reaction ofthe low molecular weight ingredient by heating the varnish along with asubstrate. Then, a portion of the interlayer insulating film formed in acircumference of the substrate is removed. In addition, a film thicknessis controlled by a spin rotation rate, rotation time, and the densityand viscosity of the varnish.

As a material of the interlayer insulating film, a material in which askeletal structure is configured by the combination of silicon (Si) andoxygen (O), and which has at least one kind of hydrogen, fluorine, analkyl group or aromatic hydrocarbon as a substituent. The interlayerinsulating film after baking can be referred to as an SiOx filmcontaining an alkyl group.

In addition, as the added inert element, one kind or plural kinds of He,Ne, Ar, Kr and Xe can be used. Above all, it is preferable to use argonsince it has the comparatively large atomic radius and is inexpensive.It is also preferable that light transmittance of the interlayerinsulating film does not decrease even when the inert element is added.The inert element may be appropriately added by using ion doping, ionimplantation or plasma treatment.

The second configuration of the invention is a light emitting devicehaving a display portion which is formed by arranging a light emittingelements between a pair of substrates, wherein the light emittingelements are connected to thin film transistors formed over onesubstrate, a high thermostability planarizing film added with an inertelement as an interlayer insulating film is formed over the thin filmtransistors, and the light emitting elements are formed over the highthermostability planarizing film.

The third configuration of the invention is a light emitting devicehaving a display portion formed by arranging light emitting elementsbetween a pair of substrates, wherein the light emitting elements areconnected to thin film transistors formed over one substrate, a highthermostability planarizing film added with an inert element as aninterlayer insulating film is formed over the thin film transistors, asource electrode or a drain electrode of the thin film transistor isconnected to an active layer through an opening portion provided in thehigh thermostability planarizing film, the opening portion has a taperedshape and added with the inert element, and the light emitting elementis formed over the high thermostability planarizing film.

As for the above-mentioned second or third configuration, the pair ofsubstrates are fixed to each other with a sealant surrounding acircumference of the display portion, and an edge portion of the highthermostability planarizing film has a tapered shape and added with aninert element.

In addition, as for each above-mentioned configuration, the inertelement contained in the high thermostability planarizing film is withinthe concentration range from 1×10¹⁹ atoms/cm³ to 5×10²¹ atoms/cm³,typically, from 2×10¹⁹ atoms/cm³to 2×10²¹ atoms/cm³.

In addition, as for each above-mentioned configuration, a taper angle atan edge portion of the high thermostability planarizing film is morethan 30° and less than 75°. However, when the inert element is added byusing plasma treatment or oblique doping, a side surface of the highthermostability planarizing film can be modified without forming theedge portion to have a tapered shape.

In addition, as for each above-mentioned configuration, the sealantcovers the side surface of the edge portion of the high thermostabilityplanarizing film, or surrounds a circumference of the highthermostability planarizing film. When the sealant is arranged so as tocover the side surface of the edge portion of the high thermostabilityplanarizing film, an EL display device with high reliability can beobtained by shielding intruding moisture or oxygen which causesdeterioration of properties of an EL element without enlarging an ELdisplay device.

In each above-mentioned configuration, the light emitting device isapplicable to both an active matrix type and a passive matrix type.

Further, a light emitting element (an EL element) has a layer containingan organic compound achieving luminescence (Electro Luminescence)generated by applying an electric field, an anode, and a cathode. Theluminescence in the organic compound includes luminescence(fluorescence) in returning from a singlet excited state to the groundstate and luminescence (phosphorescence) in returning from a tripletexcited state to the ground state. A light emitting device fabricatedaccording to the invention is applicable to both cases of usingluminescence.

A light emitting element (an EL element) having an EL layer isconstituted by a structure in which the EL layer is sandwiched between apair of electrodes and the EL layer is normally constructed by alaminated structure. Typically, there is pointed out a laminatedstructure of “hole transporting layer/light emitting layer/electrontransporting layer.” The structure is provided with very highluminescence efficiency and currently, almost all the light emittingdevices on which research and development has been progressed withadopting the structure.

Further, otherwise, it may be a structure of laminating a hole injectinglayer, a hole transporting layer, a light emitting layer, and anelectron transporting layer, or a hole injecting layer, a holetransporting layer, a light emitting layer, an electron transportinglayer, and an electron injecting layer, constructed in this order overan anode. The light emitting layer may be doped with a fluorescentpigment or the like. Further, all of the layers may be formed by using alow molecular weight material or using a high molecular weight material.In addition, a layer containing an inorganic material may be used.Further, in the specification, all the layers provided between a cathodeand an anode are generally referred to as EL layers. Therefore, all ofthe hole injecting layer, the hole transporting layer, the lightemitting layer, the electron transporting layer and the electroninjecting layer are included in the EL layers.

In the light emitting device according to the invention, the drivingmethod for screen display is not especially limited. For example, adot-sequential driving method, a line-sequential driving method, or aplane-sequential driving method can be used for the driving. Typically,the line-sequential driving method is used, and a time-division grayscale driving method or an area gray scale driving method may also beused appropriately. In addition, a video signal for inputting into asource line of the light emitting device may be an analog signal or adigital signal. A driving circuit or the like may be appropriatelydesigned in accordance with the video signal.

The fourth configuration regarding a manufacturing method is a methodfor manufacturing a light emitting device having a thin film transistorand a light emitting element over a substrate having an insulatingsurface, wherein the method for manufacturing the light emitting deviceincludes the steps of: forming a thin film transistor having asemiconductor layer having a source region, a drain region and a channelforming region therebetween, a gate insulating film and a gate electrodeover a first substrate having an insulating surface; forming a highthermostability planarizing film over unevenness shape caused by thethin film transistor; forming an opening portion which has a side with atapered shape, and is located over the source region or the drainregion, and a circumference having a tapered shape by selectivelyremoving the high thermostability planarizing film; adding an inertelement to the high thermostability planarizing film; forming a contacthole which reaches the source region or the drain region by selectivelyremoving the gate insulating film; forming an electrode which reachesthe source region or the drain region and an anode; forming a layercontaining an organic compound over the anode; forming a cathode overthe layer containing the organic compound; sealing the light emittingelement by attaching a second substrate to the first substrate with asealant surrounding a circumference of the light emitting element.

The fifth configuration of the invention regarding a manufacturingmethod is a method for manufacturing a light emitting device having athin film transistor and a light emitting element over a substratehaving an insulating surface, wherein the method for forming the lightemitting device includes the steps of: forming a thin film transistorhaving a semiconductor layer having a source region, a drain region anda channel forming region therebetween, a gate insulating film and a gateelectrode over a first substrate having an insulating surface; forming ahigh thermostability planarizing film over unevenness shape caused bythe thin film transistor; forming a contact hole which has a side with atapered shape and reaches the source region or the drain region, and acircumference having a tapered shape by selectively removing the highthermostability planarizing film; adding an inert element to the highthermostability planarizing film; forming an electrode and an anodewhich reaches the source region or the drain region; forming a layercontaining an organic compound over the anode; forming a cathode overthe layer containing the organic compound; and sealing the lightemitting element by attaching a second substrate to the first substratewith a sealant surrounding a circumference of the light emittingelement.

As for the above-mentioned fourth and fifth configurations, the highthermostability planarizing film is an SiOx film containing an alkylgroup formed by application. The step of adding the inert element to thehigh thermostability planarizing film in the configurations 4 and 5 isperformed by ion doping, ion implantation or plasma treatment.

The sixth configuration of the invention is a semiconductor deviceincluding a display portion formed by arranging thin film transistorsbetween a pair of substrates, wherein a high thermostability planarizingfilm to which an inert element is formed over the thin film transistorsas an interlayer insulating film, a source electrode or a drainelectrode of the thin film transistor is connected to an active layerthrough an opening portion provided in the high thermostabilityplanarizing film, and the opening portion has a tapered shape and addedwith an inert element.

According to the sixth configuration, the pair of substrates are fixedto each other with a sealant surrounding a circumference of the displayportion, and an edge portion of the high thermostability planarizingfilm has a tapered shape and added with an inert element.

The seventh configuration of the invention is a semiconductor deviceincluding a display portion formed by arranging thin film transistorsbetween a pair of substrates, wherein a high thermostability planarizingfilm in which a surface is modified by an inert element is formed overthe thin film transistors as an interlayer insulating film, and a sourceelectrode or a drain electrode of the thin film transistor is connectedto an active layer through an opening portion provided in the highthermostability planarizing film.

The present invention is applicable to any TFT structure. For instance,the invention can be applied to a top gate TFT, a bottom gate (inverselystaggered) TFT or a staggered TFT.

As an active layer of the TFT, an amorphous semiconductor film, asemiconductor film containing a crystal structure, a semiconductorcompound film containing an amorphous structure can be appropriatelyused. Further, a semi-amorphous semiconductor film which issemiconductor having an intermediate structure of an amorphous structureand a crystal structure (including single crystal and polycrystal), anda tertiary state which is stable energetically, and including acrystalline region having a short distance order and lattice distortion(also referred to as a microcrystal semiconductor film) can be used asthe active layer of the TFT. In the semi-amorphous semiconductor film, acrystal grain having a grain diameter from 0.5 nm to 20 nm is includedin at least one region of the film, and in the Raman spectrum, the peakspecific to silicon shifts to the lower side of wave number of 520 cm⁻¹.In addition, in the semi-amorphous semiconductor film, a diffractionpeak of (111) and (220) derived from a Si crystal lattice is observed inx-ray diffraction. The semi-amorphous semiconductor film includeshydrogen or halogen at least 1 atom % as a neutralizer of an uncombinedhand (a dangling bond). The semi-amorphous semiconductor film ismanufactured by performing glow discharging decomposition (plasma CVD)of a silicide gas. As the silicide gas, SiH₄, additionally, Si₂H₆,SiH₂Cl₂, SiHCl₃, SiCl₄, SiF₄ or the like can be used. The silicide gasmay be diluted with H₂, or H₂ and one or more of rare gas elements: He,Ar, Kr, and Ne. Dilution ratio is within the range from 2 times to 1000times. Pressure is roughly within the range from 0.1 Pa to 133 Pa; powerfrequency, from 1 MHz to 120 MHz, preferably from 13 MHz to 60 MH; andsubstrate heating temperature, at most 300° C., preferably from 100° C.to 250° C. An atmospheric constitution impurity such as oxygen, nitrogenor carbon as an impurity element within a film is preferably at most1×10²⁰ atoms/cm³, in particular, oxygen concentration is at most 5×10¹⁹atoms/cm³, preferably, at most 1×10¹⁹ atoms/cm³. Note that electricfield-effect mobility μ of a TFT in using a semi-amorphous film as anactive layer is from 1 cm²/Vsec to 10 cm²/Vsec.

According to a high thermostability planarizing film of the invention,an orientation defect of a liquid crystal can be prevented byeliminating unevenness due to a gate electrode or a semiconductor layerin a liquid crystal display device. The high thermostability planarizingfilm can have high light transmittance and preferable displayproperties.

In addition, in a light emitting device using a layer containing anorganic compound as a light emitting layer, reliability is improved byproviding an interlayer insulating film which has the small amount ofdehydration and degasification, and a structure in which moisture,oxygen, or the like is prevented from passing through the interlayerinsulating film from outside and intruding into an organic EL elementwithout enlarging the light emitting device.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A to 1D show manufacturing steps of a light emitting device.

FIGS. 2A to 2C show sectional views and a top view of a light emittingdevice.

FIGS. 3A and 3B are sectional views of a light emitting device.

FIGS. 4A to 4C are sectional views of a light emitting element.

FIGS. 5A to 5C are views showing an application apparatus and an edgeremover.

FIG. 6 is a view showing a formation flow of a high thermostabilityplanarizing film.

FIGS. 7A to 7C are views showing flows of addition steps of an inertelement.

FIGS. 8A and 8B are views showing a sectional and a periphery portion ofa light emitting device (Embodiment 1).

FIG. 9 is a view showing an enlarged illustration of a periphery portion(Embodiment 2).

FIGS. 10A and 10B are views showing cross sectionals of a light emittingdevice (Embodiment 3).

FIG. 11 is a view showing an active matrix liquid crystal display device(Embodiment 4).

FIGS. 12A to 12G are views showing examples of an electronics device.

FIG. 13 is a view showing an example of an electronics device.

DETAILED DESCRIPTION OF THE INVENTION Embodiment Mode

An embodiment mode of the present invention is described hereinafter.

A base insulating film 11 is formed over a substrate 10. As thesubstrate 10, a glass substrate, a quartz substrate, a siliconsubstrate, a metal substrate or a stainless steel substrate with aninsulating film formed on its surface may be used. A plastic substratedurable to the processing temperature may also be used.

As the base insulating film 11, an insulating film such as a siliconoxide film, a silicon nitride film or a silicon oxynitride film may beused. Although a two-layer structure is used for the base insulatingfilm 11 in this embodiment mode, a structure having a single layer film,or two or more laminated layers of the insulating films may be used.Note that the base insulating film need not be formed particularly.

Then, a semiconductor layer is formed over the base insulating film. Thesemiconductor layer is obtained by forming a semiconductor film havingan amorphous structure by a known method (sputtering, LPCVD, plasma CVD,or the like), crystallizing the semiconductor film by knowncrystallization treatment (laser crystallization, thermalcrystallization, thermal crystallization using a catalyst such asnickel, or the like), and patterning the crystalline semiconductor filmto have a desired shape using a first photomask. The semiconductor layeris formed to have a thickness from 25 nm to 80 nm (preferably, from 30nm to 70 nm). There is no particular limit to a material for thecrystalline semiconductor film; however, the crystalline semiconductorfilm may be preferably made of silicon, a silicon-germanium (SiGe) orthe like.

In addition, a continuous oscillation laser may be used forcrystallization treatment of the semiconductor film having the amorphousstructure. When crystallizing the amorphous semiconductor film, it ispreferable that second to fourth harmonics of a fundamental wave may beapplied by using a solid laser in which continuous oscillation ispossible to obtain a crystal with a large grain diameter. Typically, thesecond harmonic (532 nm) or the third harmonic (355 nm) of an Nd: YvO₄laser (a fundamental wave, 1064 nm) may be applied. When the continuousoscillation laser is used, laser light radiated from a continuousoscillation YvO₄ laser of output of 10 W is converted to harmonic by anonlinear optical element. There is also a method for radiating harmonicby putting a YvO₄ crystal and the nonlinear optical element in aresonator. Then, the harmonic is preferably formed so as to have arectangular or elliptical shape on an irradiated surface by an opticalsystem and an object to be processed is irradiated therewith. At thistime, the energy density of about from 0.01 MW/cm² to 100 MW/cm²(preferably from 0.1 MW/cm² to 10 MW/cm²) is required. The semiconductorfilm may be irradiated by being moved relatively to the laser light atthe speed of about from 10 cm/s to 2000 cm/s.

Subsequently, an insulating film 12 covering the semiconductor layer isformed after removing the resist mask. The insulating film 12 is formedto have a thickness of from 1 nm to 200 nm by using plasma CVD orsputtering. Preferably, the insulating film 12 is formed by performingsurface nitriding treatment with the use of plasma by an microwave afterforming a monolayer or a laminated structure of the insulating filmincluding silicon to have a thin thickness of 10 nm to 50 nm.

In this way, when the plasma CVD is used for forming the insulating filmthin in thickness, it is necessary to obtain the thin thickness withgood controllability by latening a formation rate. For example, thedeposition speed of the silicon oxide film can be set at 6 nm/min whenRF power is set at 100 W, 10 kHz; pressure, 0.3 Torr; an N₂O gas flow,400 sccm; and an SiH₄ gas flow, 1 sccm. The nitriding treatment with theuse of the plasma by the microwave is performed with the use of amicrowave source (2.45 GHz) and a nitrogen gas which is a reactive gas.

Note that the nitrogen concentration decreases as departing from thesurface of the insulating film 12. Because of this, the surface of thesilicon oxide film can be nitrided at high concentrations. In addition,deterioration of device properties can be prevented by reducing nitrogenof the interface between the silicon oxide film and an active layer. Inaddition, the insulating film 12 having the surface treated withnitriding functions as a gate insulating film of a TFT.

Next, a conductive film is formed over the insulating film 12 to have athickness of 1 from 100 nm to 600 nm. Here, a conductive film includinga laminate of a TaN film and a W film is formed by using sputtering. Thelaminate of the TaN film and the W film is cited here as the conductivefilm, but it is not limited hereto. As for the conductive film, amonolayer containing an element of Ta, W, Ti, Mo, Al or Cu, an alloymaterial or a compound material containing the above element as its maincomponent, or a laminate of the monolayers can be used. A semiconductorfilm typified by a polycrystalline silicon film in which an impurityelement such as phosphorous is doped may be also used.

Subsequently, a resist mask is formed by using a second photomask, andetching is performed by wet etching or dry etching. In the etching step,the conductive film is etched to obtain conductive layers 14 a, 14 b, 15a, and 15 b. In addition, the conductive layers 14 a and 14 b functionas a gate electrode of the TFT, and the conductive films 15 a and 15 bfunction as a terminal electrode.

Next, a resist mask is newly formed by using a third photomask afterremoving the resist mask. A first doping step is performed to dope animpurity element which imparts n-type conductivity (typically,phosphorus or As) to a semiconductor at low concentrations to form ann-channel TFT not shown herein. The resist mask covers a region which isto serve as a p-channel TFT and a region adjacent to the conductivelayer. A low concentration impurity region is formed by this firstdoping step through the insulating film. Although a plurality of TFTsare used to drive one light emitting element, the above-mentioned dopingstep is not necessary when the light emitting element is driven by onlyp-channel TFTs.

Then, a resist mask is newly formed by using a fourth photomask afterremoving the resist mask. A second doping step is performed to dope animpurity element which imparts p-type conductivity (typically, boron) toa semiconductor at high concentrations. P-type high concentrationimpurity regions 17 and 18 are formed by performing doping through theinsulating film 12 by the second doping step.

Then, a resist mask is newly formed by using a fifth photomask. A thirddoping step is performed to dope an impurity element which impartsn-type conductivity (typically, phosphorus or As) to a semiconductor athigh concentrations to form an n-channel TFT not shown herein. The thirddoping step is performed under the condition that the amount of doze isset at from 1×10¹³ atoms/cm² to 5×10¹⁵ atoms/cm²; and the accelerationvoltage, from 60 kV to 100 kV. The resist mask covers a region whichserves as a p-channel TFT and a region adjacent to the conductive layer.An n-type high concentration impurity region is formed by performingdoping through the insulating film 12 by the third doping step.

Afterwards, activation and hydrogenation of the impurity element addedto the semiconductor layer are performed after removing the resist maskand forming an insulating film containing hydrogen 13. The insulatingfilm containing hydrogen 13 is formed with the use of a silicon nitrideoxide film (an SiNO film) obtained by PCVD. In addition, gettering whichreduces nickel concentration in a channel formation region can be alsoperformed at the same time as activation, when the semiconductor film iscrystallized by using a metal element which promotes crystallization,which is typically nickel.

Then, a high thermostability planarizing film 16 which serves as aninterlayer insulating film is formed. As the high thermostabilityplanarizing film 16, an insulating film in which a skeletal structure isformed by the combination of silicon (Si) and oxygen (O) obtained byapplication is used.

Here, a formation procedure of the high thermostability planarizing film16 is described in detail with reference to FIGS. 5A to 5C and FIG. 6.

First, pure water washing of a substrate to be processed is performed.Megasonic washing may be performed. Next, after performing dehydrobakingfor 110 seconds at 140° C., a temperature of the substrate is regulatedby cooling for 120 seconds with a water-cooled plate. Next, thesubstrate is transferred to and placed in a spinning applying apparatusshown in FIG. 5A.

FIG. 5A shows a section schematic diagram of the spinning applyingapparatus. In FIG. 5A, reference numeral 1001 denotes a nozzle; 1002, asubstrate; 1003, an application cup; and 1004, an application materialsolution. The spinning applying apparatus has a mechanism in which thesolution of a material to be applied is dropped from the nozzle 1001,and the substrate 1002 is placed horizontally in the application cup1003 and the entire application cup rotates. The spinning applyingapparatus also has a mechanism in which the pressure of atmosphere inthe application cup 1003 can be controlled.

Next, pre-wet application is performed to improve wettability with theuse of an organic solvent such as thinner (a volatile mixture solventformed by mixing aromatic hydrocarbon (toluene or the like), alcohols,ester acetate or the like). Thinner is thrown off by spinning thesubstrate with high speed (rotation rate, 450 rpm), after spreading thethinner thoroughly with centrifugal force by spinning the substrate(rotation rate 100 rpm) as dropping 70 ml of the thinner.

Subsequently, the solution of the material to be applied prepared bydissolving siloxane system polymer in a solvent (propyleneglycolmonomethyl ether) is thoroughly spread by centrifugal force withgradually spinning (rotation rate from 0 rpm to 1000 rpm) the substrateand dropping the solution of the material to be applied from the nozzle1001. Then, the substrate is gradually spun (rotation rate from 0 rpm to1400 rpm) after holding the substrate for 30 seconds for leveling a filmformed by the application step.

Inside of the application cup 1003 is exhausted to decompress, thenreduced-pressure drying is performed for within 1 minute.

Edge removing treatment is performed by an edge remover equipped in thespinning applying apparatus shown in FIG. 5A. An edge remover 1006equipped with a means for moving which moves in parallel along theperiphery of the substrate 1002 is shown in FIG. 5B. In the edge remover1006, a thinner spraying nozzle 1007 as in FIG. 5C is provided tosandwich one side of the substrate, and a circumference of theapplication film 1008 is dissolved by the thinner. Thereby removing thefilm formed by the application step in the circumference of thesubstrate edge face by exhausting liquid and gas in the arrow directionshown in the figure.

Then, prebaking is performed by performing baking for 170 seconds at110° C.

A flow diagram showing the above-mentioned procedure is shown in FIG. 6.

The substrate is transferred from the spinning applying apparatus andcooled. Then, baking is further performed for 1 hour at 270° C. Thus,the high thermostability planarizing film 16 is formed (FIG. 1A).

In addition, the high thermostability planarizing film 16 may be formedby ink-jet A material solution can be saved with the use of ink-jet.

The high thermostability planarizing film 16 in a circumference isremoved at the same time as forming a contact hole in the highthermostability planarizing film 16 with the use of a sixth mask. Here,etching (wet etching or dry etching) is performed under the condition inwhich a desirable selective ratio can be obtained with respect to theinsulating film 13. Although there is no limit to an etching gas to beused, CF₄, O₂, He and Ar is suitable to use. Dry etching is performed bysetting the flow of CF₄ at 380 sccm; O₂, 290 sccm; He, 500 sccm; Ar, 500sccm; RF power, 3000 W; and pressure, 25 Pa. In addition, the etchingtime may be increased at the rate of about from 10% to 20% for etchingthe insulating film 13 without leaving a residue on its surface. Onetime etching or plural times of etching may be conducted to obtain atapered shape. Here, the tapered shape is obtained by performing thesecond time etching with the use of CF₄, O₂, and He by setting the flowof CF₄ at 550 sccm; O₂, 450 sccm; He, 350 sccm; RF power, 3000 W; andpressure, 25 Pa (FIG. 1B).

Next, doping treatment with an inert element is performed to form ahighly densified part 20 on the surface of the high thermostabilityplanarizing film 16 (FIG. 1C). The doping treatment may be performed byion doping or ion implantation. Typically, argon (Ar) is used as theinert element. Distortion is given by adding the inert element with acomparatively large atomic radius to modify a surface (including a sidesurface) or to highly densify for preventing the intrusion of moistureor oxygen. The inert element contained in the highly densified part 20is set within the concentration range from 1×10¹⁹ atoms/cm³ to 5×10²¹atoms/cm³, typically, from 2×10¹⁹ atoms/cm³ to 2×10²¹ atoms/cm³. Inaddition, the side surface of the high thermostability planarizing film16 is formed to have a tapered shape so as to be doped. It is desirableto set the taper angle θ more than 30° and less than 75°.

Here, although an application step or a doping step is performedaccording to the flow shown in FIG. 7C, the flow is not particularlylimited to this order. For example, as shown in FIG. 7A, doping of aninert element may be performed after sequentially performing a materialsolution application, reduced-pressure drying and baking. In addition,as shown in FIG. 7B, baking may be performed after performing a materialsolution application, reduced-pressure drying and doping of an inertelement. However, the inert element is not doped enough into the sidesurface of an opening portion or the side surface of an edge portion insteps shown in FIGS. 7A and 7B. Therefore, it is preferable to add aprocess in which doping is further performed from an oblique directionor an inert element is added to the side surface of an opening portionor the side surface of the edge portion.

Corona treatment plasma treatment or coupling agent treatment may beperformed before or after formation of the high thermostabilityplanarizing element 16 to improve adhesiveness. In addition, two or morekinds of treatment of the corona treatment, the plasma treatment or thecoupling agent treatment can be combined, and in this case, thetreatment sequence is not particularly limited.

Then, etching is performed using the high thermostability planarizingfilm 16 as a mask, and the exposed insulating films 12 and 13 areselectively removed. The etching treatment of the insulating films 12and 13 is performed by using CHF₃ and Ar for etching gases. Note thatthe etching time may be increased at the rate about from 10% to 20% inorder to perform etching without leaving a residue over thesemiconductor layer.

Next, wirings 21 and 22 are formed by performing etching with the use ofan eighth mask after forming a conductive film (FIG. 1D).

Subsequently, a first electrode 23, in other words, an anode (or acathode) of an organic light emitting element is formed with the use ofa ninth mask. A film containing a substance of Ti, TN, TiSi_(x)N_(y),Ni, W, WSi_(x), WN_(x), WSi_(x)N_(y), NbN, Mo, Cr, Pt, Zn, Sn, In or Mo,an alloy material or a compound material containing the substance as itsmain component, or a laminate of the films may be used as the firstelectrode 23 within the range from 100 nm to 800 nm thick in total.

In addition, in the case of a bottom emission light emitting deviceshown in FIG. 4B, or a light emitting device shown in FIG. 4C, as thematerial of the first electrode, a transparent conductive film (ITO(indium tin oxide), ITSO, zinc oxide (ZnO), IZO (indium zinc oxide), inwhich zinc oxide from 2 [%] to 20 [%] is mixed into indium oxide.

Subsequently, an insulator 29 (referred to as a bank, a partition wall,a barrier, or the like) is formed using a tenth mask to cover an edgeportion of the first electrode 23. An insulator 29 can include aninorganic material (silicon oxide, silicon nitride, silicon oxynitride,or the like), a photosensitive or non-photosensitive organic material(polyimide, acryl, polyamide, polyimideamide, a resist, orbenzocyclobutene), an SOG film (for example, an SiOx film including analkyl group) obtained by application, or a laminate of these films. Forinstance, in the case that positive photosensitive acrylic is used as amaterial for an organic resin, it is preferable to give a curved surfacewith a radius of curvature only to a top edge portion of the insulator.Both a negative photosensitive material that is insoluble in an etchantunder light and a positive photosensitive material that is soluble in anetchant under light can be used for the insulator.

Next, a layer containing an organic compound 24 is formed by evaporationor application. It is preferable to perform vacuum heating beforeforming the layer containing an organic compound 24, thereby performingdeaeration, in order to improve reliability. For example, it ispreferable to perform heat treatment at a temperature from 200° C. to300° C. under a reduced pressure atmosphere or an inert atmosphere inorder to remove gas contained in the substrate, before evaporating anorganic compound material. In the case of employing evaporation to formthe layer containing an organic compound 24, a film formation chamber isevacuated to have a vacuum of at most 5×10⁻³ Torr (0.665 Pa), preferablyfrom 10⁻⁴ Torr to 10⁻⁶ Torr. The organic compound is preliminarilyvaporized by resistance heating in evaporating. The vaporized organiccompound is scattered in the direction of the substrate by opening ashutter at the time of evaporation. The vaporized organic compound isscattered upwardly and is evaporated on the substrate through an openingportion provided for a metal mask.

For example, white light emission can be achieved by sequentiallylaminating Alq₃, Alq₃ partially doped with Nile red, which is a redlight emitting pigment, p-EtTAZ, and TPD (aromatic diamine) withevaporation.

In the case of forming the layer containing an organic compound byapplication using spin coating, an applied layer is preferably baked byvacuum heating after application. For example, an aqueous solution ofpoly (ethylene dioxythiophene)/poly (styrene sulfonic acid), namely,(PEDOT/PSS), may be applied to an entire surface and baked to form afilm that serves as a hole injection layer. Then, a polyvinyl carbazole(PVK) solution doped with a luminescent center pigment (such as1,1,4,4-tetraphenyl-1,3-butadiene (TPB),4-dicyanomethylene-2-methyl-6-(p-dimethylamino-styryl)-4H-pyran (DCM1),Nile red, or coumarin 6) may be applied to the entire surface and bakedto form a film that serves as a light emitting layer. The solvent ofPEDOT/PSS is water and PEDOT/PSS is not soluble in an organic solvent.Accordingly, the hole injection layer is in no danger of dissolvingagain even in the case of applying PVK over the PEDOT/PSS. Since thesolvents used for PEDOT/PSS and PVK are different from each other, it ispreferable not to use the same film formation chambers. The layercontaining an organic compound 24 can be formed to have a single layer.In this case, a 1,3,4-oxadiazole derivative (PBD) capable oftransporting electrons may be dispersed in polyvinyl carbazole (PVK)capable of transporting holes. In addition, white light emission canalso be obtained by dispersing 30 wt % of PBD as an electrontransporting agent and dispersing four kinds of pigments (TPB, coumarin6, DCM1, and Nile red) in appropriate amounts.

The layer containing an organic compound may include layers separatelyformed with colors of R, G, and B, respectively, to perform full colordisplay in one panel.

Thereafter, a second electrode 25 made of a conductive film, that is, acathode (or an anode) of an organic light emitting element is formed. Afilm formed of an alloy such as MgAg, MgIn, AlLi, a compound such asCaF₂, or CaN, or a film formed of an element belonging to Group 1 or 2in the periodic table, and aluminum by co-evaporating may be used as thesecond electrode 25.

In the case of a top emission light emitting device which emits lightthrough the second electrode as shown in FIG. 4A, or in the case of alight emitting device shown in FIG. 4C, an aluminum film or an aluminumfilm that contains a minute amount of Li, having a thickness from 1 nmto 10 nm is used. When employing an Al film for the second electrode 25,it becomes possible to form a material in contact with the layercontaining an organic compound 24 with a material other than oxide,thereby reliability of the light emitting device can be improved.Further, a light transmitting layer (film thickness from 1 nm to 5 nm)containing CaF₂, MgF₂, or BaF₂ may also be formed as a cathode bufferlayer before forming the aluminum film having a thickness from 1 nm to10 nm.

Subsequently, a transparent protective layer 26 is formed by evaporationor sputtering. The transparent protective layer 26 protects the secondelectrode 25.

Next, the light emitting element is sealed by attaching a sealingsubstrate 33 with a sealant 28. The sealing substrate is attached sothat the sealant 28 covers an edge portion (tapered portion) of the highthermostability planarizing film 16. Note that a region surrounded bythe sealant 28 is filled with a transparent filler 27. There is noparticular limitation on the filler 27 as long as the filler is a lighttransmitting material. Typically, an ultraviolet curable epoxy resin ora heat curable epoxy resin may be used. Here, a highly thermostable UVepoxy resin (product name: 2500 Clear, manufactured by ElectroliteCooperation) may be used, which has an index of refraction of 1.50,viscosity of 500 cps, Shore D hardness of 90, tensile strength of 3000psi, a Tg point of 150° C., volume resistivity of 1×10¹⁵ Ω·cm, andwithstand voltage of 450 V/mil. In addition, total transmittance can beimproved by filling interspace between a pair of substrates with thefiller 27.

Lastly, an FPC 32 is attached to an terminal electrode 35 with ananisotropic conductive film 31 by a known method. A transparentconductive film is preferably used as the terminal electrode 35 and isformed over terminal electrodes 15 a and 15 b formed simultaneously witha gate wiring (FIG. 2A).

FIG. 2B is an enlarged view of a peripheral portion. A taper angle θ isset at more than 30° and less than 75°.

FIG. 2C is a top view. An edge portion 34 of the high thermostabilityplanarizing film is covered with the sealant 28 as shown in FIG. 2C. Across-sectional view taken along a chained line A-B in FIG. 2Ccorresponds to FIG. 2A.

FIG. 3A shows a state of connection between the second electrode 26 anda wiring 35 in a lower layer. The wiring 35 is connected to terminalelectrodes 15 c and 15 d. FIG. 3B shows a part of a driver circuitportion composed of an n-channel TFT 36 and a p-channel TFT 37.

An active matrix light emitting device manufactured in this way, has atapered shape in an edge portion or an opening portion, in the highthermostability planarizing film 16, typically, an interlayer insulatingfilm (a film which serves as a base film of a light emitting elementlater) in which a skeletal structure is configured by the combination ofsilicon (Si) and oxygen (O). Further, distortion is given by adding aninert element with the comparatively large atomic radius to modify ordensify the surface (including a side surface) for preventing theintrusion of moisture or oxygen. Thereby, reliability of the lightemitting device is promoted.

The present invention having the above embodiment is described in moredetail later in the following embodiments.

Embodiment 1

In this embodiment, an example of an edge portion covered with a metallayer is described with reference to FIGS. 8A and 8B. Portions otherthan a peripheral portion are identical with those in FIG. 2A shown inEmbodiment Mode; therefore, detailed description is omitted here. Notethat the same reference numerals are used in FIGS. 8A and 8B for thesame parts as those in FIG. 2A.

Metal layers 621 and 622 are formed by covering a circumference of ahigh thermostability planarizing film. The metal layers 621 and 622 maybe formed simultaneously with source/drain electrodes 21 and 22, or maybe separately formed by patterning. However, a part of a lead wiring tobe connected to a terminal electrode is not covered with the metallayers 621 and 622, although not shown here.

FIG. 8B shows an enlarged cross-sectional view of an peripheral portion.A side surface of an edge portion having a step in the highthermostability planarizing film 16 is covered with the metal layers 621and 622. Coverage is favorable since the edge portion has a taperedshape. Further, adhesiveness with the metal layer is also favorablesince an inert element is added to a surface of the thermostabilityplanarizing film 16 and a highly densified portion 20 is formed.

In this embodiment, intrusion of moisture or the like can be furtherprevented by covering a side surface of an edge portion added with aninert element and having a tapered shape with the metal layers 621 and622.

This embodiment can be freely combined with Embodiment Mode.

Embodiment 2

In this embodiment, an example of an edge portion added with an inertelement by plasma treatment is described with reference to FIG. 9.Portions other than the edge portion are identical with those in FIG. 2Bshown in Embodiment Mode; therefore, detailed description is omittedhere. Note that the same reference numerals are used in FIG. 9 for thesame parts as those in FIG. 2B.

This embodiment is an example of forming a highly densified portion on asurface (including a side surface) by adding an inert element withoutforming an edge portion of a high thermostability planarizing film 16into a tapered shape.

In this embodiment, an edge portion of the high thermostabilityplanarizing film 16 is nearly perpendicular, and has curvature in a topedge portion thereof.

The highly densified portion can be provided on a surface (including aside surface) by a method for adding an inert element with plasmatreatment even if an edge portion has such a shape as shown in FIG. 9.

According to this embodiment, a sealing structure that effectivelyprevents intrusion of moisture or the like can be achieved withoutperforming etching for forming a tapered shape.

This embodiment can be freely combined with Embodiment Mode orEmbodiment 1.

Embodiment 3

An example of an inversely staggered TFT is described in this embodimentwith reference to FIGS. 10A and 10B. Portions other than a TFT and aterminal electrode are identical with those in FIG. 2A shown inEmbodiment Mode; therefore, detailed description is omitted here. Notethat the same reference numerals as those in FIG. 2A are used in FIGS.10A and 10B for the same parts as those in FIG. 2A.

A TFT shown in FIG. 10A is a channel stop type. A gate electrode 719 anda terminal electrode 715 are simultaneously formed, and a semiconductorlayer containing an amorphous semiconductor film 714 a, an n+ layer 718,and a metal layer 717 are laminated over a gate insulating film 12. Achannel stopper 714 b is formed over a portion to be a channel formationregion of the semiconductor layer 714 a. Further, source/drainelectrodes 721 and 722 are formed.

A TFT shown in FIG. 10B is a channel etch type. A gate electrode 819 anda terminal electrode 815 are simultaneously formed, and a semiconductorlayer containing an amorphous semiconductor film 814, an n+ layer 818,and a metal layer 817 are laminated over a gate insulating film 12. Aportion to be a channel formation region of the semiconductor layer 814is thinly etched. Further, source/drain electrodes 821 and 822 areformed.

A semi-amorphous semiconductor film (referred to also as a microcrystalsemiconductor film) which has an intermediate structure between anamorphous structure and a crystalline structure (including singlecrystal and poly crystal) and has a third condition being stable interms of free energy and includes a crystalline region havingshort-distance order and lattice distortion can also be used in place ofthe amorphous semiconductor film. As a method for manufacturing asemi-amorphous semiconductor film, glow discharge decomposition (plasmaCVD) of a silicide gas is performed. As a silicide gas, SiH₄, or inaddition, Si₂H₆, SiH₂Cl₂, SiHCl₃, SiCl₄, SiF₄, or the like can be used.The silicide gas may be diluted with H₂, or H₂ and one or more kinds ofrare gas elements: He, Ar, Kr, and Ne. Dilution ratio is within therange from 2 times to 1000 times. Pressure is roughly within the rangefrom 0.1 Pa to 133 Pa; power supply frequency, from 1 MHz to 120 MHz,preferably from 13 MHz to 60 MHz; and a substrate heating temperature,at most 300° C., preferably from 100° C. to 250° C. An atmosphericconstituent impurity such as oxygen, nitrogen, or carbon as an impurityelement within a film is preferably at most 1×10²⁰ atom/cm⁻³, andparticularly, oxygen concentration is at most 5×10¹⁹ atoms/cm³,preferably at most 1×10¹⁹ atoms/cm³. Note that electric field-effectmobility μ of a TFT using a semi-amorphous semiconductor film as anactive layer is from 1 cm²/Vsec to 10 cm²/Vsec.

This embodiment can be freely combined with Embodiment Mode, Embodiment1, or Embodiment 2.

Embodiment 4

In this embodiment, an example of an active matrix liquid crystaldisplay device is described with reference to FIG. 11.

An example of manufacturing steps is described hereinafter.

First, an active matrix substrate is formed by using a lighttransmitting substrate 600. A large-sized substrate having a size of,for example, 600 mm×720 mm, 680 mm×880 mm, 1000 mm×1200 mm, 1100 mm×1250mm, 1150 mm×1300 mm, 1500 mm×1800 mm, 1800 mm×2000 mm, 2000 mm×2100 mm,2200 mm×2600 mm, or 2600 mm×3100 mm is preferably used; therefore, themanufacturing cost is reduced. A glass substrate containing bariumborosilicate glass, aluminoborosilicate glass, or the like, as typifiedby #7059 glass or #1737 glass produced by Coming Inc. can be used as asubstrate that can be used. In addition, a light transmitting substratesuch as a quartz substrate or a plastic substrate can be alternativelyused.

After a conductive layer is formed entirely over the substrate 600having an insulating surface by sputtering, a first photolithographystep is performed to form a resist mask. An unnecessary part of theresist mask is etched away, thereby forming a wiring and an electrode (agate electrode, a storage capacitor wiring, a terminal, and the like).Note that a base insulating film is formed over the substrate 600, ifnecessary.

An element of Ti, Ta, W, Mo, Cr, or Nd, an alloy containing the elementsas its component, or a nitride containing the elements as its componentmay be used as a material of the wiring and the electrode. Further, alaminate including a plurality of layers each including a substanceselected from elements of Ti, Ta, Ta, W, Mo, Cr, and Nd, an alloycontaining the elements as its component, or a nitride containing theelements as its component.

When a screen size is enlarged, the length of each wiring is increased.A problem of high wiring resistance occurs and the power consumption isincreased. Accordingly, the wiring and the electrode may contain amaterial of Cu, Al, Ag, Au, Cr, Fe, Ni, or Pt, or an alloy thereof tolower the wiring resistance and to achieve the low power consumption.Further, the wiring and the electrode may be formed with ink jet byusing liquid in which ultrafine particles (grain diameter from 5 nm to10 nm) of metal such as Ag, Au, Cu, or Pd are separately dispersed inhigh concentration without being aggregated.

Subsequently, a gate insulating film is entirely formed by PCVD. Thegate insulating film is formed by laminating a silicon nitride film anda silicon oxide film to have a thickness from 50 nm to 200 nm,preferably 150 nm. Note that the gate insulating film is not limited toa laminate, and an insulating film such as a silicon oxide film, asilicon nitride film, a silicon oxynitride film, a tantalum oxide film,or the like can be used alternatively.

Next, a first amorphous semiconductor film is formed entirely over thegate insulating film by a known method such as plasma CVD or sputteringto have a thickness from 50 nm to 200 nm, preferably from 100 nm to 150nm. Typically, an amorphous silicon (a-Si) film is formed to have athickness of 100 nm. When the film is formed over a large-sizedsubstrate, the chamber is also enlarged; therefore, more treating timefor evacuating the chamber and a large amount of film formation gas arerequired. Thus, further cost reduction may be realized by forming theamorphous silicon (a-Si) film by using a linear plasma CVD apparatusunder the atmospheric pressure.

Thereafter, a second amorphous semiconductor film including an impurityelement imparting one conductivity type (n-type conductivity or p-typeconductivity) is formed to have a thickness from 20 nm to 80 nm. Thesecond amorphous semiconductor film including an impurity elementimparting one conductivity type (n-type conductivity or p-typeconductivity) is entirely formed by a known method such as plasma CVD orsputtering. In this embodiment, the second amorphous semiconductor filmincluding an n-type impurity element is formed by sputtering using asilicon target added with phosphorus.

Next, a resist mask is formed by a second photolithography step, and anunnecessary portion is etched away, thereby forming a firstisland-shaped amorphous semiconductor film and a second island-shapedamorphous semiconductor film. As a method for etching on this occasion,wet etching or dry etching is carried out.

After a conductive layer covering the second island-shaped amorphoussemiconductor film is formed by sputtering, a third photolithographystep is performed to form a resist mask. An unnecessary portion isetched away, thereby forming a wiring and an electrode (a source wiring,a drain electrode, a storage capacitor electrode, and the like). Anelement of Al, Ti, Ta W, Mo, Cr, Nd, Cu, Ag, Au, Fe, Ni, or Pt, or analloy containing the elements as its component may be used as a materialof the wiring and the electrode. Further, the wiring and the electrodemay be formed with ink jet by using liquid in which ultrafine particles(grain diameter from 5 nm to 10 nm) of metal such as Ag, Au, Cu, or Pdare separately dispersed in high concentration without being aggregated.When the wiring and the electrode are formed by ink jet, thephotolithography step is unnecessary, so that further cost reduction canbe achieved.

Subsequently, a resist mask is formed by a fourth photolithography step,and a source wiring, a drain electrode, and a capacitor electrode areformed by etching an unnecessary portion away. As a method for etchingon this occasion, wet etching or dry etching is carried out. A storagecapacitor having an insulating film containing the same material as thatof the gate insulating film as a dielectric is formed. A part of thesecond amorphous semiconductor film is removed in a self-alignmentmanner by using the source wiring and the drain electrode as masks, andfurther, a part of the first amorphous semiconductor film is thinned.The thinned area serves as a channel formation region of a TFT.

A protective film (not shown) containing a silicon nitride film with athickness of 150 nm and a high thermostability planarizing film 1609with a thickness of 1 μm are entirely formed by plasma CVD. The highthermostability planarizing film 1609 is baked after applying a liquidraw material called varnish in which a low molecular weight ingredient(a precursor) having the combination of silicon (Si) and oxygen (O) isdissolved into a solvent over the substrate by spin coat or ink jet. Thehigh thermostability planarizing film 1609 has higher lighttransmittance than acryl, and is suitable for an interlayer insulatingfilm of a liquid crystal display device.

Subsequently, the high thermostability planarizing film 1609 in acircumference is removed at the same time of forming a contact hole inthe high thermostability planarizing film 1609.

Thereafter, doping treatment using an inert element is performed to forma highly densified portion 1619 over a surface of the highthermostability planarizing film 1609. As a doping treatment, ion dopingor ion implantation is carried out. Typically, argon (Ar) is used as theimpurity element. Distortion is given by adding the inert element withthe comparatively large atomic radius to modify a surface (including aside surface) or to highly densify for preventing the intrusion ofmoisture or oxygen; therefore, deterioration of a liquid crystal isprevented.

Then, a channel etch TFT is manufactured by hydrogenation.

Note that a channel etch type is described as an example of a TFTstructure in this embodiment; however, the structure is not limitedthereto. Any one of the structures of a channel stopper TFT, a top gateTFT, and a staggered TFT may be employed.

Next, a transparent electrode film that contains ITO (indium tin oxide),an indium oxide—zinc oxide alloy (In₂O₃—ZnO), or zinc oxide (ZnO) isformed to be 110 nm thick. Thereafter, a pixel electrode 1601 is formedby a photolithography step and an etching step.

Thus, an active matrix substrate including a source wiring, an inverselystaggered TFT and a storage capacitor in a pixel portion, and a terminalportion can be manufactured.

Rubbing treatment is performed after an alignment film 1623 is formedover the active matrix substrate. In this embodiment, a columnar spacer1602 for maintaining a gap between substrates is formed in a desiredposition by patterning an organic resin film such as an acrylic resinfilm. Further, spherical spacers may be scattered all over the substratein place of the columnar spacer.

Subsequently, a counter substrate is prepared. The counter substrate isprovided with a color filter 1620 in which colored layers and lightshielding layers are disposed correspondingly to each pixel. Aplanarizing film is provided to cover the color filter and the lightshielding layer. Subsequently, a counter electrode 1621 made of atransparent conductive film is formed over the planarizing film tooverlap the pixel portion. An alignment film 1622 is formed entirelyadjacent to the counter substrate, and then, rubbing treatment isperformed.

After a sealant is drawn to surround the pixel portion of the activematrix substrate, liquid crystal is discharged onto the regionsurrounded with the sealant under reduced pressure by a liquid crystaldispenser device. Thereafter, the active matrix substrate and thecounter substrate are attached to each other with a sealant 1607 underreduced pressure, without being exposed to atmospheric air. The twosubstrates are sealed by being attached to each other so that thesealant 1607 covers an edge portion (tapered portion) of the highthermostability planarizing film 1609. The sealant 1607 is mixed with afiller (not shown). The two substrates are attached to each other withthe filler and the columnar spacer 1602 so that the substrates have auniform interval. By employing a method for dropping a liquid crystal,the amount of liquid crystal used in a manufacturing process can bereduced, and particularly, the cost can be considerably reduced when alarge-seized substrate is used.

Thus, an active matrix liquid crystal display device is completed. Ifnecessary, the active matrix substrate or the counter substrate is cutinto a desired shape. Further, an optical film such as a polarizingplate 1603 or a color filter is appropriately provided using a knowntechnique. An FPC is further attached to the substrate by using a knowntechnique.

An active matrix liquid crystal display device (transmissive type) iscompleted by providing a liquid crystal module obtained according to theabove steps with a backlight 1604 and an optical waveguide 1605 andcovering the liquid crystal module with a cover 1606. A part of across-sectional view of the active matrix liquid crystal display deviceis shown in FIG. 8B. Note that the cover and the liquid crystal moduleare fixed with an adhesive or an organic resin. The polarizing plate1603 is attached to both the active matrix substrate and the opposingsubstrate, since the liquid crystal display device is a transmissivetype.

Further, an example of the transmissive type is described in thisembodiment; however, the liquid crystal display device is not limitedthereto, and a reflective or semi-transparent liquid crystal displaydevice can be manufactured. In the case of obtaining a reflective liquidcrystal display device, a metal film with high optical reflectance,typically, a film containing aluminum or silver as its main component, alaminate thereof, or the like may be used for a pixel electrode.

This embodiment can be freely combined with Embodiment Mode.

Embodiment 5

In this embodiment, examples of electronic devices equipped with adisplay portion are described with reference to FIGS. 12A to 12G andFIG. 13. An electronic device having a liquid crystal display device ora light emitting device can be completed by applying the presentinvention.

Examples of electronic devices are as follows: a video camera; a digitalcamera; a goggle type display (head mounted display); a navigatingsystem; an audio reproducing device (car audio, an audio component, orthe like); a laptop personal computer; a game machine; a personaldigital assistant (a mobile computer, a cellular phone, a portable gamemachine, an electronic book, or the like); and an image reproducingdevice including a recording medium (specifically, a device capable ofprocessing data in a recording medium such as a Digital Versatile Disk(DVD) and having a display that can display the image of the data); andthe like.

FIG. 12A is a perspective view of a laptop personal computer, and FIG.12B is a perspective view thereof in a folded state. The laptop personalcomputer includes a main body 2201, a casing 2202, display portions 2203a and 2203 b, a keyboard 2204, an external connection port 2205, apointing mouse 2206, and the like. By applying the invention to thedisplay portions 2203 a and 2203 b, a high thermostability planarizingfilm of which surface is added with an inert element effectivelyprevents intrusion of moisture or an impurity from external, and alaptop personal computer with high reliability can be completed.

FIG. 12C shows a television, which includes a casing 2001, a supportingsection 2002, a display portion 2003, a video input terminal 2005, andthe like. The television includes all television for displayinginformation, including ones for personal computers, for TV broadcastingreception, and for advertisement. By applying the invention to thedisplay portion 2003, a high thermostability planarizing film of whichsurface is added with an inert element has high planarity over an entirepanel even in a large size. Consequently, a television that indicates avivid display can be completed.

FIG. 12D shows a portable game machine, which includes a main body 2501,a display portion 2505, an operation switch 2504, and the like. Byapplying the invention to the display portion 2505, intruding moistureor oxygen that is a cause of deteriorating characteristics of an ELelement can be blocked without enlarging the display portion.Accordingly, a portable game machine with high reliability, having asmall display portion, can be completed.

FIG. 12E is a perspective view of a cellular phone, and FIG. 12F is aperspective view thereof in a folded state. The cellular phone includesa main body 2701, a casing 2702, display portions 2703 a and 2703 b, anaudio input portion 2704, an audio output portion 2705, operation keys2706, an external connection port 2707, an antenna 2708, and the like.

The cellular phone shown in FIGS. 12E and 12F is provided with ahigh-resolution display portion 2703 a that mainly displays an image infull color and an area color display portion 2703 b that mainly displayscharacters and symbols. By applying the invention to the displayportions 2703 a and 2703 b, intruding moisture or oxygen that is a causeof deteriorating characteristics of an EL element can be blocked withoutenlarging the display portion. Accordingly, a cellular phone having alightweight and small display portion can be completed.

FIG. 12G shows a display board such as an advertisement board, whichincludes display portion 2801, a casing 2802, a lighting portion 2803such as LED light, and the like. By applying the invention to thedisplay portion 2801, a display board that indicates a bright displaycan be completed since a high thermostability planarizing film of whichsurface is added with an inert element has high light transmittance.

FIG. 13 shows an example of mounting a display portion on an automobile.Here, an automobile is used as a typical example of a vehicle, but theinvention is not particularly limited thereto. It goes without sayingthat the invention can be applied to an aircraft, a train, an electrictrain, or the like. As for a display device mounted particularly on anautomobile, emphasis is put on high reliability even in a severeenvironment (inside of an automobile which is subject to hightemperatures and high humidity).

FIG. 13 shows the vicinity of a driver's seat in an automobile. Adashboard 2301 is provided with audio reproducing devices, specificallya car audio system and a car navigating system. A main body 2401 of thecar audio system includes a display portion 2402 and operation switches2403 and 2404. By applying the invention to the display portion 2402, ahigh thermostability planarizing film of which surface is added with aninert element effectively prevents intrusion of moisture or an impurityfrom external. Consequently, a car audio system with high reliabilitycan be completed.

By applying the invention further to a display portion 2300 of the carnavigating system, intrusion of moisture or an impurity from externalcan be effectively prevented. Consequently, a car navigation system withhigh reliability can be completed.

By applying the invention further to a display portion 2305 displayingan air condition state in an automobile, intrusion of moisture or animpurity from external can be effectively prevented. Consequently, a carnavigation system with high reliability can be completed.

Further, in the vicinity of a steering wheel portion 2302, the dashboard2301 is provided with a display portion 2303 in which a digital displayof a measuring instrument such as a speedometer is formed. By applyingthe invention to the display portion 2303, a high thermostabilityplanarizing film of which surface is added with an inert elementeffectively prevents intrusion of moisture or an impurity from external.Consequently, a machinery indicator with high reliability can becompleted.

Further, an on-board car audio system and a car navigation system aredescribed in this embodiment; however, the invention may be applied toother vehicle indicators and to stationary audio and navigating systems.

A light emitting device or a liquid crystal display device obtained byapplying the invention as mentioned above may be used for displayportions of various electronic devices. Note that a semiconductor devicemanufactured by employing any one of structures of Embodiment Mode, andEmbodiments 1 to 4 may be used for an electronic device of thisembodiment.

A high thermostability planarizing film (typically, an SiOx filmincluding an alkyl group) obtained by application according to theinvention prevents intrusion of moisture or oxygen by performing dopingusing an impurity element to modify or density a surface (including aside surface).

The high thermostability planarizing film according to the invention canbe made into an interlayer insulating film durable to reflow treatmentin multilayer wirings.

1. A semiconductor device, comprising: an insulating film formed over afirst substrate, wherein an edge portion of the insulating film has atapered shape; a metal layer covering the edge portion; a sealantcovering the metal layer and the edge portion; a second substrate overthe sealant, and wherein the first substrate and the second substrateare attached with the sealant, and wherein the sealant is formeddirectly on the metal layer.
 2. The semiconductor device according toclaim 1, wherein the insulating film is a silicon oxide film includingan alkyl group.
 3. The semiconductor device according to claim 1,wherein a taper angle at the edge portion of the insulating film is morethan 30° and less than 75°.
 4. A semiconductor device, comprising: aninsulating film formed over a first substrate, wherein an edge portionof the insulating film has a tapered shape and is added with an inertelement; a metal layer covering the edge portion; a sealant covering themetal layer and the edge portion; a second substrate over the sealant,and wherein the first substrate and the second substrate are attachedwith the sealant.
 5. The semiconductor device according to claim 4,wherein the insulating film is a silicon oxide film including an alkylgroup.
 6. The semiconductor device according to claim 4, wherein a taperangle at the edge portion of the insulating film is more than 30° andless than 75°.
 7. The semiconductor device according to claim 4, whereinthe inert element is one selected from the group consisting of He, Ne,Ar, Kr and Xe.
 8. A semiconductor device, comprising: an insulating filmformed over a first substrate, wherein an edge portion of the insulatingfilm has a tapered shape and is added with an inert element; a metallayer covering the edge portion; a light emitting element formed overthe insulating film; a sealant covering the metal layer and the edgeportion; a second substrate over the sealant, the second substratecovering the light emitting element, and wherein the first substrate andthe second substrate are attached with the sealant.
 9. The semiconductordevice according to claim 8, wherein the insulating film is a siliconoxide film including an alkyl group.
 10. The semiconductor deviceaccording to claim 8, wherein a taper angle at the edge portion of theinsulating film is more than 30° and less than 75°.
 11. Thesemiconductor device according to claim 8, wherein the inert element isone selected from the group consisting of He, Ne, Ar, Kr and Xe.